The DNS is the core Internet system responsible for mapping domain names, such as, for example, www.example.com, to service related details such as internet protocol (hereinafter “IP”) addresses, email servers, internet-accessible resources and the like. An authoritative DNS server or service is a DNS system with definitive information about specific domain names and/or DNS records. The authoritative DNS server is queried by users or intermediary servers to obtain service details for the domain names for which it is authoritative.
Historically, authoritative DNS servers respond to DNS queries by doing lookups and/or inquiries in a simple, static database mapping domain names and record types to service details. For example, the canonical BIND name server software, produced by the Internet Systems Consortium, uses “zone files” encoding DNS record details for records in a DNS “zone,” such as, for example, domain and/or subdomain.
More recently, some DNS server software, or managed DNS service providers with proprietary software, have added capabilities for computing answers to DNS queries dynamically, instead of performing a simple lookup in a static database to determine the answer to a query, these software and/or systems may gather a collection of possible answers from a database or other source of input. Based upon configuration details and other inputs, such as, for example, the IP address of the requester or system status details of backend services or servers, the system selects one or more answers dynamically to determine the response to the query. Such software or systems generally provide a small set of predefined approaches for computing dynamic answers to a DNS query based on limited, mostly static inputs.